Orthodontic adhesive formulations utilized in the past for bonding stainless steel or plastic orthodontic brackets to tooth surfaces have generally been of the following types:
(1) a blend of an aromatic diacrylate with an aliphatic diacrylate, cured with a conventional catalyst-accelerator system;
(2) a blend of methyl methacrylate monomer with poly(methyl methacrylate) polymer using a peroxide or trialkyl borane curing catalyst;
(3) an aromatic diacrylate system containing a conventional ultraviolet-sensitive accelerator, cured with an ultraviolet ray gun, or,
(4) a blend of an ester of methacrylic acid with a monoalcohol containing at least one epoxy group and finely divided filler material, in combination with a conventional catalyst-accelerator curing system.
The first three types of prior art adhesives are characterized by relatively poor water resistance, poor peel resistance, and poor retention to tooth enamel in orthodontic applications. These first three types of adhesive also are characterized by relatively poor adhesion to stainless steel (mesh) surfaces such as are found on stainless steel orthodontic brackets, and to polycarbonate plastics, of which orthodontic brackets are frequently made today. Adhesives in the fourth category are generally superior with respect to all of these characteristics, but may in some cases produce toxic reactions if contact is made with the skin.
Consequently, there is a need for new orthodontic adhesive formulations that possess the desired characteristics for such applications and that offer a choice of adhesive products to the dental profession and to the public.
There is also a need for adhesives for general purpose applications, where the adhesives are characterized by relatively high strength and fast setting times. Such adhesives are particularly useful in industrial applications involving the bonding of metals to plastics, and for bonding glass to the surfaces of other materials as in many electronic devices.